Power converters need to be protected against when a line-to-ground fault occurs.
According to a technology disclosed in Patent Literature 1, contactors are connected to respective ends of a secondary winding in a transformer, and these contactors are opened when a line-to-ground fault occurs. According to this technology, by opening the two contactors, a line-to-ground fault current does not flow into the transformer, thereby preventing the transformer from being damaged.
Patent Literatures 2 to 5 disclose technologies of detecting a line-to-ground fault. The technology disclosed in Patent Literature 2 installs a current detector, and assumes that the line-to-ground fault has occurred when the current detector detects a current, and shuts off a breaker connected to an overhead line. According to this technology, power supply from the overhead line is broken by opening the breaker, and thus circuits can be protected.
According to the technology disclosed in Patent Literature 3, a wire on the positive side of a transformer and a wire on a negative side of the transformer are connected to a current detector so as to allow the current flowing through both wires to flow in the same direction. According to this technology, the current does not flow through the current detector when a line-to-ground fault occurs at the negative side of the transformer, and thus the line-to-ground fault at the negative side of the transformer can be detected.
According to the technology disclosed in Patent Literature 4, an essential load and a power supply device are connected via a breaker, and a normal load and the power supply device are connected via a specific breaker. According to this technology, the breaker trips when the line-to-ground fault occurs at the essential load, and the specific breaker trips when the line-to-ground fault occurs at the normal load. According to this technology, even if the line-to-ground fault occurs at the one load, the power can be continuously supplied to the other load.
According to the technology disclosed in Patent Literature 5, a residual current transformer is installed, and when the residual current transformer detects a current, a breaker connected to a main line for supplying power from a transforming station is opened. According to this technology, the current flowing from the main line is broken by opening the breaker, thereby protecting high-voltage power receiving equipment.